Vacuum Tube Furnace: Selection Guide & Published Specs

Q: What is a vacuum tube furnace used for?

Published applications across the HuanYu tube range are vacuum sintering, annealing, degassing, debinding, reduction, calcination, carbonisation of carbon products, CVD research and substrate coating. The multi-position vacuum platform is published specifically for heat treatment of metal materials under low vacuum, reduction and protective atmospheres.

Q: What temperature can a vacuum tube furnace reach?

It depends entirely on the tube material. Published HuanYu tube configurations run 600/950 °C in the single-zone platform, 1100–1800 °C in the two-zone platform, 1200/1400/1600 °C on the multi-position vacuum platform, up to 1700 °C on the vertical platform and the GSL/GZG high-vacuum range, and 2000 °C with one model at 2300 °C on the vacuum carbon tube range. The main site also publishes vacuum carbon tube sintering models at 2100 °C and 2400 °C.

Q: What vacuum level does a vacuum tube furnace achieve?

Published HuanYu figures span three bands. The multi-position vacuum platform is published with a stated maximum vacuum of **5 Pa**, which suits purge-and-backfill, low-vacuum annealing and carbonisation. The infrared tube furnace is published at **6.67 × 10⁻² Pa** with a mechanical + diffusion pump set and **6.67 × 10⁻³ Pa** with a mechanical + molecular pump set. The vacuum carbon tube range is published at **6.67 × 10⁻³ Pa** ultimate with a pressure-rise rate of **≤ 2 Pa/h**.

Q: Quartz or alumina tube — which should I choose?

Choose quartz when the process runs below its band and you value transparency and fast ramping; the published `GL1200-S` tops out at 1200 °C (< 0.5 h) with ≤ 1100 °C continuous. Choose corundum when the process needs to go higher; the published `GL1700-S` and `GL1700C` reach 1700 °C with ≤ 1600 °C continuous. Above that, the tube material changes to carbon, and the platform changes with it.

Q: Can a vacuum tube furnace run hydrogen?

Yes, and HuanYu publishes a dedicated `Hydrogen Reduction Tube Furnace` at 1200 / 1100 °C configurations in vacuum or controlled atmosphere. Hydrogen is a different safety class from inert gas, and published HuanYu hydrogen platforms include multi-stage explosion protection. The published multi-position platform also carries an outlet combustion nozzle able to vent hydrogen, argon, nitrogen, oxygen and carbon monoxide.

Q: How do I choose between single-zone, multi-zone and multi-position?

Zone count controls the temperature *profile* along the tube — use two or three zones when the process needs a gradient, as in vapour transport or two-stage reaction work. Multi-position is a different axis: it gives several independent sample positions inside one furnace body so a single run produces a controlled comparison. If your problem is reproducibility across samples rather than a thermal gradient, multi-position is the answer.

Q: How accurate is temperature control?

Published HuanYu tube platforms list **±1 °C** class control accuracy (the multi-position platform publishes ±1 °C display accuracy and ±5 °C temperature-field stability; the three-zone opening furnace publishes ±1 °C over 50 programmable segments). Control accuracy and field stability are separate specifications and should be quoted and tested separately.

Q: Do I need a diffusion pump or a molecular pump?

Only if the process needs high rather than rough or medium vacuum. The published infrared tube furnace illustrates the step directly: the same furnace is offered at **6.67 × 10⁻² Pa** on a mechanical + diffusion set or **6.67 × 10⁻³ Pa** on a mechanical + molecular set. For a great deal of tube furnace work the vacuum exists to remove air before an inert backfill, and a mechanical pump is sufficient.

Q: Can a vacuum tube furnace be customised?

Yes. HuanYu publishes customisation scope across chamber and tube size, heating system, atmosphere, vacuum train, controls, cooling, tooling and safety interlocks, and publishes configuration-dependent values as "configuration specific" rather than supplying a default. Published tube sizes already span Φ25 mm to Φ320 mm, and the tilting rotary furnace is published as configurable from 1.5 to 15 kW.

Q: How do I verify vacuum performance before accepting delivery?

Require a pressure-rise test, not just an ultimate-vacuum reading. Measure the pressure rise over a defined interval, both empty and loaded. Published rise-rate references from HuanYu are **≤ 2 Pa/h** on the vacuum carbon tube range (brochure pp. 19–20) and **≤ 0.67 Pa/h** on the high-vacuum annealing and brazing platform (brochure p. 35). ---

Short answer

A vacuum tube furnace heats samples inside a sealed process tube — quartz, alumina or carbon — connected to a pump set and gas feed, so the load can run under vacuum, under a controlled flowing atmosphere, or under vacuum followed by a gas backfill. Tube geometry delivers a small, fast-responding, highly uniform hot zone.

Specification summary

Specifying a vacuum tube furnace means resolving six coupled decisions at once. (1) Tube material, because it caps the usable temperature before the heating element does: quartz to roughly 1200 °C, alumina (corundum) to about 1700 °C, carbon or graphite well beyond that (general engineering ranges). (2) Vacuum level, from rough vacuum around 10³ Pa for purge-and-backfill work to 10⁻³ Pa or better for oxygen-sensitive sintering. (3) Tube diameter and heated length, sized on the sample plus its boat or fixture. (4) Zone count, single, two or multi-zone, which sets how precisely the thermal profile can be shaped along the tube. (5) Orientation — horizontal for powder beds and continuous flow, vertical for drop-quench and fibre work. (6) Atmosphere, meaning whether the tube sees inert gas, hydrogen or carbon-bearing vapour. Choose the tube material and the pumping set first; temperature follows from them.

Key facts

ItemValue

What it is

A furnace whose hot zone is a sealed process tube connected to a vacuum pump set and gas train

Tube materials seen on HuanYu units

Fused quartz · corundum (alumina) · stainless steel · carbon / graphite

Published HuanYu temperature bands

600–950 °C (single-zone) · 1100–1800 °C (two-zone) · 1200/1400/1600 °C (multi-position vacuum) · 1200–1700 °C (GSL/GZG high-vacuum) · 2000 °C and 2300 °C (vacuum carbon tube) · 2100 °C and 2400 °C (vacuum carbon tube sintering)

Published HuanYu tube sizes

Quartz Φ25–100 mm × 600–1400 mm · corundum Φ50–100 mm × 800–1000 mm · carbon tube Φ90 × 120 mm to Φ320 × 600 mm

Published vacuum figures

5 Pa on the multi-position vacuum tube platform · 6.67 × 10⁻² Pa with mechanical + diffusion pump and 6.67 × 10⁻³ Pa with mechanical + molecular pump on the infrared tube furnace · 6.67 × 10⁻³ Pa ultimate with ≤ 2 Pa/h pressure rise on the vacuum carbon tube range

Heating elements by temperature band

HRE alloy / Kanthal wire (to ~1200 °C) · silicon carbide rods (~1400 °C) · molybdenum disilicide (~1700 °C) · graphite (2000 °C+) (general engineering ranges)

Typical applications

Vacuum sintering · annealing · degassing · debinding · reduction · carbonisation of carbon products · CVD research · substrate coating

HuanYu published configurations

Multi-Position Vacuum Tube Furnace (1200/1400/1600 °C) · Vacuum Carbon Tube Furnace ZKT-25-20 · Vacuum Carbon Tube Sintering Furnace VCF-270-21 / VCF-58-24 / VCF-80-21 · High-vacuum tube furnace GSL/GZG · Infrared Tube Furnace · Vertical Tube Furnace (up to 1700 °C)

Company footing

Founded 2009 · 60 product series · 500+ product models · ~200 units/year capacity · ISO 9001:2015 / GB/T 19001-2016 (cert. U25Q2SH8002817R3M)

What is a vacuum tube furnace, and what does it actually do?

Strip away the enclosure and a vacuum tube furnace is three subsystems bolted together. Understanding which one your process actually constrains is what prevents an expensive re-specification.

1. The process tube and its seals. This is the defining part. The tube — quartz, corundum or carbon — is the pressure boundary and the chemical barrier between the hot zone and the outside world. It is closed at both ends by flanges or compression fittings. On the published GSL / GZG high-vacuum tube furnace range the tube is sealed at both ends with stainless-steel flanges, with a float flowmeter controlling the inlet gas flow (brochure pp. 13–14). That detail matters more than it looks: the flange is where vacuum performance is either kept or lost.

2. The hot zone and its heating elements. For a tube furnace, the heating element choice is dictated by the tube material and the target temperature, not chosen independently. The published HuanYu tube programme traces this directly: HRE alloy wire or Kanthal resistance wire in the 1200 °C GL1200-S, silicon carbide rods in the 1400/1500 °C GL1400 and GL1500 configurations, molybdenum disilicide rods in the 1700 °C GL1700-S and GL1700C, and graphite in the 2000–2300 °C vacuum carbon tube range (brochure pp. 01–04 and pp. 19–20).

3. The pumping train and gas train. A vacuum tube furnace is only as good as the pumps behind it. Published HuanYu figures show the step clearly: the infrared tube furnace is offered with a mechanical + diffusion pump set giving 6.67 × 10⁻² Pa, or a mechanical + molecular pump set giving 6.67 × 10⁻³ Pa (brochure pp. 11–12), while the vacuum carbon tube range is published at an ultimate vacuum of 6.67 × 10⁻³ Pa with a pressure-rise rate of ≤ 2 Pa/h (brochure pp. 19–20). The gas train — flowmeter, wash inlets, outlet — decides what happens after the pump has done its work.

The practical consequence: a tube furnace is not "a vacuum furnace in tube shape". It is a process window defined by the intersection of tube material, element material and pump set. Change one and the other two usually have to move.

Which tube material do you need — quartz, alumina or carbon?

This is the first decision, and it is the one buyers most often make second. The tube material sets the ceiling for everything downstream, because it has to survive the peak temperature while staying chemically compatible with whatever is inside it.

Tube materialPractical temperature bandVacuum suitabilityWhere it failsGeneral engineering ranges

Fused quartz

To ~1200 °C, and it softens rather than melting sharply

Excellent for rough to medium vacuum; transparent, so the load is visible

Devitrifies and deforms above its band; reacts with carbon and with hot hydrogen

Fast-ramp lab work, CVD research, optical monitoring, low-mass samples

Alumina / corundum

~1400–1700 °C

Very good; the standard choice where quartz runs out

Thermally shock-sensitive — fracture on fast ramps is a known failure mode

Sintering, calcination, clean oxide work, higher-temperature CVD

Stainless steel retort

Up to ~1100 °C in continuous service

Good for vacuum and for positive-pressure gas work

Creeps and oxidises at high temperature; can catalyse reactions

Strong-atmosphere operation, larger loads, industrial tube systems

Carbon / graphite

2000 °C and above

Designed for high vacuum; the tube is the hot zone

Cannot tolerate oxygen or water vapour at temperature

Ultra-high-temperature sintering, refractory carbides, graphite processing

The published HuanYu tube range follows exactly this ladder:

✓Quartz. GL1200-S and GL1200-S-II are published at a maximum of 1200 °C for < 0.5 h with a continuous rating of ≤ 1100 °C, using quartz tubes of Φ25 × 600 mm or Φ50 × 600 mm with a 200 mm heated zone (100 + 100 mm in the dual-zone version), 1.5 kW on 220 V, ±1 °C control accuracy and a recommended ramp of ≤ 10 °C/min (brochure pp. 01–02). The published high-vacuum GSL1200/GZG1200 models use quartz tubes of Φ60, Φ80 or Φ100 mm × 1000 mm at 3 kW with a working temperature of 1100 °C against a 1200 °C maximum (brochure pp. 13–14).
✓Alumina. The published GL1700-S reaches 1700 °C for < 0.5 h with ≤ 1600 °C continuous in corundum tubes of Φ50 × 800 mm or Φ60 × 800 mm with a 170 mm heated zone at 2.5 kW; the larger GL1700C runs corundum tubes of Φ60, Φ80 or Φ100 × 1000 mm with a 300 mm heated zone at 6 kW (brochure pp. 03–04). The GSL1400/GSL1700 high-vacuum models use corundum tubes of Φ60–100 mm × 1000 mm at 4 kW, published at 1400 °C (working 1300 °C) with silicon carbide elements and 1700 °C (working 1600 °C) with molybdenum disilicide (brochure pp. 13–14).
✓Stainless steel. The published infrared tube furnace accepts a quartz tube or a stainless-steel tube, which is the published expression of the same trade-off: quartz for visibility and purity, steel for atmosphere strength (brochure pp. 11–12).
✓Carbon. Beyond the tube-furnace family proper, the published vacuum carbon tube range moves to a graphite tube with graphite heating, Φ90 × 120 mm up to Φ320 × 600 mm (brochure pp. 19–20).

Two practical notes that the published data makes visible. First, peak and continuous ratings are different numbers — quartz at 1200 °C peak is ≤ 1100 °C continuous, corundum at 1700 °C peak is ≤ 1600 °C continuous. Quoting only the peak is the single most common specification error. Second, the published heating rates drop as temperature rises — ≤ 10 °C/min below 1400 °C, falling to ≤ 5 °C/min above it on the corundum platforms (brochure pp. 01–04). That is not a control limitation; it is the tube protecting itself from thermal shock.

Where does a vacuum tube furnace sit in the vacuum scale?

Vacuum level and vacuum purpose are different things, and confusing them is the second most common specification error. For a large share of tube furnace work, the vacuum is not there to reach a physics-grade low pressure — it is there to remove air so that a subsequent inert-gas backfill is clean.

As a general engineering frame, not a HuanYu specification, vacuum is conventionally banded:

RegimePressure (absolute)Typical pump setTypical tube furnace use

Rough vacuum

10⁵–10² Pa

Single rotary-vane mechanical pump

Purge-and-backfill, debinding, oxidation-limited annealing

Medium vacuum

10²–10⁻¹ Pa

Two-stage mechanical, or mechanical plus roots

General vacuum annealing, degassing, carbonisation of carbon products

High vacuum

10⁻¹–10⁻⁴ Pa

Mechanical plus diffusion or molecular pump

Bright annealing, reactive metals, oxygen-sensitive powder sintering, brazing

Ultra-high vacuum

< 10⁻⁴ Pa

Turbomolecular or ion pumps

Surface science; rarely a furnace requirement

The bands above are general engineering ranges published across the vacuum industry and are included as orientation only. They are not a HuanYu product specification.

Read against that scale, the published HuanYu tube figures span the middle of the range. The Multi-Position Vacuum Tube Furnace page states plainly that the platform can pump vacuum and that "the higher vacuum can reach 5 Pa", while the same page describes the furnace as intended for heat treatment of metal materials under low vacuum, reduction and protective atmospheres, and for special materials such as the carbonisation process of carbon products. 5 Pa is a medium-vacuum number — perfectly adequate for purging, for low-vacuum annealing and for carbonisation work, and not the right instrument for bright annealing of a reactive metal.

If the process genuinely needs a low absolute pressure, the specification moves platform. The published high-vacuum options on the HuanYu tube range are the GSL/GZG high-vacuum tube furnaces (brochure pp. 13–14) and, at the far end, the vacuum carbon tube range at 6.67 × 10⁻³ Pa ultimate (brochure pp. 19–20).

The number buyers forget is pressure-rise rate. Ultimate vacuum tells you how low a chamber can go on its best day. Pressure-rise rate — published in Pa/h — tells you how fast it re-contaminates from outgassing, leaks and the insulation inside the hot zone. Published HuanYu references are ≤ 2 Pa/h on the vacuum carbon tube range (brochure pp. 19–20) and ≤ 0.67 Pa/h on the high-vacuum annealing and brazing platform (brochure p. 35). A furnace can hit a deep vacuum and still be unsuitable. Ask for both numbers, and ask for the rise test to be run loaded, not just empty.

How many zones — and horizontal or vertical?

Zone count and orientation are the two choices that change what the furnace can do, rather than how hot it gets.

Zone count controls the shape of the thermal profile

A single-zone furnace gives one uniform hot zone. Multi-zone furnaces exist so the temperature can vary along the tube, which is what a vapour-transport, gradient-annealing or two-stage reaction process needs.

The published HuanYu range covers the whole ladder:

✓Single zone — Single-Zone Tube Furnace is published at 600 / 950 °C configurations.
✓Two zone — Two-Zone Tube Furnace is published at 1100 / 1400 / 1600 / 1800 °C configurations for air or controlled thermal processing; the GL1200-S-II dual-zone splits a 200 mm heated length into 100 + 100 mm with independent control per zone (brochure pp. 01–02).
✓Three zone — the published three-zone opening tube furnace runs at 1100 °C maximum for < 0.5 h, holding two Φ50 × 1000 mm quartz tubes, with a 470 mm heated zone split 150 + 170 + 150 mm and a 50-segment programmable controller at ±1 °C (brochure pp. 11–12). Note the published detail that the second and third zones carry 30 mm insulating dividers while the first two do not — that is how a real gradient is built.
✓Multi-position — a distinct idea: several independent sample positions inside one furnace body, so a single run produces a controlled comparison. The published Multi-Position Vacuum Tube Furnace is offered at 1200 / 1400 / 1600 °C rated configurations with a double-layer water-cooled shell, an external closed water-cooled vacuum tank for rapid cooling, alumina polycrystalline fibre vacuum-adsorbed insulation that the page states saves about 50% energy, and heating elements selected across silicon carbide rods, molybdenum disilicide rods or molybdenum wire. Published control figures are ±1 °C display accuracy, ±5 °C temperature-field stability and a 1–15 °C/min heating rate.

That last pair of numbers is worth pausing on. Control accuracy and temperature-field stability are different specifications and should be quoted separately. A ±1 °C controller on a ±5 °C field is a ±5 °C furnace.

Orientation solves a mechanical problem, not a thermal one

Horizontal is the default: powder beds, boats, continuous gas flow across the sample, and the easiest tube to load and support.

Vertical exists for two reasons — drop-quenching, where the sample falls from the hot zone into a quench medium, and hanging fibre or wire work where gravity is part of the process. The published Vertical Tube Furnace is offered at up to 1700 °C in vacuum or controlled atmosphere.

Two further geometries matter for powder work. The published tube sliding-rail furnace HGL1200 mounts the furnace body on rails so it can be slid off the tube for rapid heating and rapid cooling, running a quartz tube of Φ25–100 mm × 1400 mm at 3 kW and 1200 °C (brochure pp. 05–10). The published tilting rotary tube furnace runs 1200 °C with 0–40° tilt and 0–10 rpm rotation at 1.5–15 kW, configurable — the geometry that keeps a powder bed moving instead of sintering into a lump (brochure pp. 05–10).

Published HuanYu vacuum tube furnace configurations

Every row below is a value published by HuanYu, either on the main site or in the printed product brochure. Brochure citations give printed folio numbers; the brochure is a spread-format catalogue, so printed page 38 corresponds to the right half of PDF page 21.

Main-site published configurations

ConfigurationPublished temperatureTube / working zoneEnvironmentSource

Vacuum Carbon Tube Furnace ZKT-25-20

2000 / 2300 °C configurations

Carbon tube (family range Φ90 × 120 to Φ320 × 600 mm)

Vacuum-capable

/products/vacuum-carbon-tube-furnace-71

Vacuum Carbon Tube Sintering Furnace VCF-270-21

2100 °C

Vacuum carbon tube

Vacuum / protected atmosphere

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Vacuum Carbon Tube Sintering Furnace VCF-58-24

2400 °C

Vacuum carbon tube

Vacuum / protected atmosphere

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Vacuum Carbon Tube Sintering Furnace VCF-80-21

2400 °C

Vacuum carbon tube

Vacuum / protected atmosphere

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Multi-Position Vacuum Tube Furnace

1200 / 1400 / 1600 °C

Multi-position tube; external closed water-cooled vacuum tank